It is conventional wisdom among development agencies that to be effective, resource management programs must be based on local participation. This approach - usually called "community-based resource management" or CBRM - can help ensure that projects are sustainable and meet local needs. But participation takes time - attending meetings and training courses, sitting on committees, monitoring fellow villagers to see that they follow the rules, imposing penalties on those who do not. These "transactions costs" are often neglected when community projects are designed. Governments tend to assume that these costs are minimal, or that communities can easily absorb them. To see how transactions costs affect the success of community-based resource management, this study from the Philippines examined one of the country's most important coastal conservation programs. It found that these costs were quite significant, and that community groups shouldered a large proportion of them, generally without financial compensation. It also found that these costs were key determinants in the success or failure of the scheme's various projects. The study looked at the community-based coastal resource management project in San Miguel Bay (SMB-CRM). This is a pilot project in the government-initiated Fisheries Sector Program, which is intended to augment the income of small-scale fishermen and preserve coastal resources. This project was chosen because it has made considerable progress in improving fisheries management and because it highlights several management issues related to community involvement.